Sealed compressor and refrigerator including sealed compressor

ABSTRACT

A sealed compressor ( 100 ) comprises an electric component ( 110 ), a compression component ( 112 ), and a sealed container ( 102 ), the compression component includes a shaft ( 118 ), a cylinder block ( 124 ), a piston ( 130 ), and a ball bearing ( 176 ), the ball bearing includes a cage ( 168 ), a plurality of rolling elements ( 166 ); a first race ( 164 ), a second race ( 170 ), and a support member ( 172 ), and when a mass of a shaft assembly ( 118   a ) including the rotor ( 116 ) and the shaft is M, a spring constant of the support member is K, and a maximum rotational frequency of the shaft assembly is F, a relationship of F&lt;1/4π)*(K/M) − 0.5 is satisfied.

TECHNICAL FIELD

The present invention relates to a sealed compressor and a refrigerator including the sealed compressor. Particularly, the present invention relates to a sealed compressor used in a heat pump cycle such as a refrigeration cycle system, and a refrigerator including the sealed compressor.

BACKGROUND ART

Conventionally, there is known a sealed compressor intended to reduce an energy loss associated with a rotation, between a rotating shaft and a cylinder block axially supporting the shaft. For example, in a sealed compressor disclosed in Patent Literature 1, a cylinder block includes a cylinder and a radial bearing hub, and the radial bearing hub supports a crankshaft in its radial direction. The lower portion of the crankshaft is fastened to a rotor of an electric motor and the upper portion thereof has an eccentric section. The eccentric section is axially supported by the upper annular surface of the radial bearing hub via an axial ball bearing. The axial ball bearing includes a plurality of balls, a circular cage for holding the balls, upper annular race and lower annular race which sandwich the balls in a vertical direction, and a support means placed on the lower surface side of the lower annular race. The support means includes an upper contact surface and a lower contact surface, and thereby is capable of vibrating with respect to the lower annular race and the upper annular surface of the radial bearing hub.

CITATION LIST Patent Literature

Patent Literature 1: Translation of PCT Application Publication No. 2005-500476

SUMMARY OF INVENTION Technical Problem

However, in the above described conventional sealed compressor, the support means vibrating causes the crankshaft to resonate. For this reason, if the crankshaft rotates at a high speed by the rotor, and the characteristic frequency of the crankshaft and the rotational speed of the crankshaft are synchronized with each other, the crankshaft vibrates more significantly due to the resonance, which increases a noise in the sealed compressor.

The present invention is directed to solving the above described problem, and an object of the present invention is to provide a sealed compressor which can reduce an energy loss and a noise, and a refrigerator including the sealed compressor.

Solution to Problem

According to an aspect of the present invention, there is provided a sealed compressor comprising: an electric component including a stator and a rotor which is rotatable with respect to the stator; a compression component activated by the electric component; and a sealed container accommodating the electric component and the compression component; wherein the compression component includes: a shaft including a main shaft fastened to the rotor, an eccentric shaft which is eccentric with respect to the main shaft, and a flange connecting the main shaft and the eccentric shaft to each other; a cylinder block including a main bearing supporting the main shaft such that the main shaft is rotatable, and a cylinder having a compression chamber inside thereof; a piston which is coupled to the eccentric shaft and is reciprocatable within the compression chamber; and a ball bearing placed between the flange and a thrust surface of the main bearing; wherein the ball bearing includes: a cage; a plurality of rolling elements held in the cage; a first race and a second race which sandwich the rolling elements therebetween; and an elastic support member placed between the second race and the thrust surface of the main bearing; wherein when a mass of a shaft assembly including the rotor and the shaft is M, a spring constant of the support member is K, and a maximum rotational frequency of the shaft assembly is F, a relationship of F<(1/4π)*(K/M)⁻0.5 is satisfied.

Advantageous Effects of Invention

The present invention has the above described configuration, and has advantages that it is possible to provide a sealed compressor which can reduce an energy loss and a noise, and a refrigerator including the sealed compressor.

The above and further objects, features and advantages of the invention will more fully be apparent from the following detailed description of a preferred embodiment with reference to accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] FIG. 1 is a cross-sectional view showing a sealed compressor according to Embodiment 1 of the present invention.

[FIG. 2] FIG. 2 is an enlarged view showing a region A of FIG. 1.

[FIG. 3] FIG. 3 is a perspective view showing a wave washer used in a thrust ball bearing of FIG. 2.

[FIG. 4] FIG. 4 is a graph showing a frequency response function of a shaft assembly of FIG. 3.

[FIG. 5] FIG. 5 is a cross-sectional view schematically showing a refrigerator according to Embodiment 2 of the present invention.

DESCRIPTION OF EMBODIMENTS

According to a first aspect of the present invention, there is provided a sealed compressor comprising: an electric component including a stator and a rotor which is rotatable with respect to the stator; a compression component activated by the electric component; and a sealed container accommodating the electric component and the compression component; wherein the compression component includes: a shaft including a main shaft fastened to the rotor, an eccentric shaft which is eccentric with respect to the main shaft, and a flange connecting the main shaft and the eccentric shaft to each other; a cylinder block including a main bearing supporting the main shaft such that the main shaft is rotatable, and a cylinder having a compression chamber inside thereof; a piston which is coupled to the eccentric shaft and is reciprocatable within the compression chamber; and a ball bearing placed between the flange and a thrust surface of the main bearing; wherein the ball bearing includes: a cage; a plurality of rolling elements held in the cage; a first race and a second race which sandwich the rolling elements therebetween; and an elastic support member placed between the second race and the thrust surface of the main bearing; wherein when a mass of a shaft assembly including the rotor and the shaft is M, a spring constant of the support member is K, and a maximum rotational frequency of the shaft assembly is F, a relationship of F<(1/4π)*(K/M)⁻0.5 is satisfied.

In accordance with this configuration, the ball bearing placed between the eccentric shaft of the shaft and the thrust surface of the main bearing can reduce an energy loss associated with the rotation of the shaft. Since the relationship of F<(1/4π)*(K/M)⁻0.5 is satisfied, the resonance of the shaft assembly due to the support member can be prevented, and a noise generated in the sealed compressor can be reduced.

According to a second aspect of the present invention, in the sealed compressor according to the first aspect, the support member may be an annular wave washer; and the wave washer may be configured to include a plurality of convex portions protruding in a thickness direction toward the second race and a plurality of convex portions protruding in the thickness direction toward the thrust surface of the main bearing such that the convex portion protruding toward the second race and the convex portion protruding toward the thrust surface are arranged alternately.

In accordance with this configuration, because of the aligning function and elasticity of the annular wave washer, friction and plastic deformation of the balls can be prevented, and an energy loss associated with the rotation of the shaft can be reduced.

According to a third aspect of the present invention, in the sealed compressor according to the second aspect, the wave washer may be formed of a spring steel; and wherein when a diameter of the main shaft is d and a thickness of the wave washer is t, 0.1 d<t<0.3 d may be satisfied. In accordance with this configuration, the elasticity of the wave washer can be kept while lessening the thickness of the wave washer.

According to a fourth aspect of the present invention, in the sealed compressor according to any one of the first to third aspects, the electric component may be activated by one of a plurality of operation frequencies using an inverter power supply which adjusts a frequency of electric power supplied to the electric component. In accordance with this configuration, even when the electric component is operated by any one of the plurality of operation frequencies, the resonance of the shaft assembly due to the support member can be prevented.

According to a fifth aspect of the present invention, there is provided a refrigerator comprising the sealed compressor according to any one of the first to fourth aspects. In accordance with this configuration, since the resonance of the shaft assembly due to the support member can be prevented in the sealed compressor, a noise and a vibration generated in the refrigerator can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Throughout the drawings, the same or corresponding components are identified by the same reference symbols and will not be described in repetition.

Embodiment 1

FIG. 1 is a cross-sectional view showing a sealed compressor 100. For easier understanding of the description, a direction parallel to the axis of a main shaft 120 of a shaft 118 will be referred to as a longitudinal direction, while a direction which is perpendicular to the longitudinal direction will be referred to as a lateral direction.

As shown in FIG. 1, the sealed compressor 100 includes a compressor body 106 and a sealed container 102 accommodating the compressor body 106. The sealed compressor 100 is a device configured such that the compressor body 106 causes a working fluid to be in high-temperature and high-pressure states and the working fluid is discharged from the sealed container 102. The compressor body 106 includes an electric component 110 and a compression component 112 activated by the electric component 110. The compressor body 106 is elastically supported by, for example, a suspension spring 108.

The sealed container 102 is filled with lubricating oil 104 and the working fluid. The lubricating oil 104 is used for lubricating the compression component 112 for actuation and reserved in the bottom portion of the sealed container 102. As the working fluid, for example, hydrocarbon-based R600a (isobutane) which is low in global warming potential, or the like is used. A suction pipe 103 for suctioning the working fluid and a discharge pipe 105 for discharging the working fluid are connected to the sealed container 102. The sealed container 102 is provided with a power supply terminal 113 connected to the electric component 110. An inverter power supply (not shown) is connected to the power supply terminal 113.

The electric component 110 includes a stator 114 and a rotor 116 which rotates with respect to the stator 114. The stator 114 is configured such that a plurality of constituents are arranged in a substantially cylindrical shape. The constituents are configured such that copper windings are wound around a core constructed of thin plates stacked together. The windings are continuous in all of the constituents and both ends thereof are connected to the power supply terminal 113. The rotor 116 has a substantially cylindrical shape having a cylindrical space in a center portion thereof and is placed inward relative to the stator 114.

The compression component 112 is placed above the electric component 110 and includes a shaft 118 activated by the electric component 110. The shaft 118 includes a cylindrical main shaft 120. The lower end portion of the main shaft 120 is inserted into a cylindrical space and fastened to the rotor 116. The main shaft 120 is provided with an oil feeding mechanism 128. The oil feeding mechanism 128 includes, for example, a pump section (not shown) attached to the lower end portion of the main shaft 120, a penetrating path (not shown) which penetrates the main shaft 120, and a spiral groove 128 a formed on the outer peripheral surface of the main shaft 120. The lower portion of the main shaft 120 and the pump section are immersed in the lubricating oil 104 reserved in the bottom portion of the sealed container 102. The penetrating passage and the spiral groove 128 a are in communication with a region in the vicinity of the sliding portions of the compression component 112.

The shaft 118 further includes an eccentric shaft 122 and a flange 174 which are provided above the main shaft 120. The eccentric shaft 122 has a cylindrical shape and extends in parallel with the main shaft 120 such that the axis of the eccentric shaft 122 does not conform to the axis of the main shaft 120. The flange 174 is placed above the main shaft 120. The lower surface of the flange 174 is connected to the upper end of the main shaft 120. The flange 174 is placed below the eccentric shaft 122. The upper surface of the flange 174 is connected to the lower end of the eccentric shaft 122. The flange 174 joins the main shaft 120 and the eccentric shaft 122 to each other. The flange 174 has, for example, a substantially sector shape around the eccentric shaft 122 on a plane perpendicular to the eccentric shaft 122. The main shaft 120 is connected to the center portion of the flange 174. A portion of the flange 174, which has an arc portion of a substantially sector shape, protrudes in a direction opposite to the eccentric shaft 122. A main bearing 126 of a cylinder block 124 is placed below the flange 174.

The cylinder block 124 includes the main bearing 126 and a cylinder 134. The main bearing 126 has a substantially cylindrical shape extending in the longitudinal direction and has a longitudinal cylindrical space therein. The main shaft 120 is rotatably inserted into the longitudinal cylindrical space. The main bearing 126 radially supports the main shaft 120 on an inner surface thereof. The main bearing 126 bears a longitudinal load applied to the flange 174 on a thrust surface 160 as will be described later via a thrust ball bearing 176. The longitudinal load applied to the flange 174 corresponds to the weight of a shaft assembly 118 a with a mass M. The shaft assembly 118 a includes a shaft 118 including the main shaft 120, the flange 174, and the eccentric shaft 122, and the rotor 116 fastened to the main shaft 120. In a case where the shaft 118 or the rotor 116 is attached with a weight, this weight is also included in the shaft assembly 118 a.

The cylinder 134 includes therein a cylindrical space extending laterally. A valve plate 146 is attached to the end surface of the cylinder 134. The valve plate 146 closes one end of the lateral cylindrical space. Thereby, a compression chamber 148 is formed inside the cylinder 134. A cylinder head 150 is fastened to the end surface of the cylinder 134 so as to cover the valve plate 146, and a suction muffler 152 is mounted between the valve plate 146 and the cylinder head 150. The suction muffler 152 is molded using a resin such as PBT (polybutylene terephthalate), and an internal muffling space can reduce a noise generated by the working fluid flowing from the suction pipe 103.

One end portion of a piston 130 is reciprocatingly inserted into the compression chamber 148 inside the cylinder 134, while the other end portion of the piston 130 is connected to a coupling section 136 via a piston pin 138. One end portion of the coupling section 136 is connected to the piston 130, while the other end portion of the coupling section 136 is connected to the eccentric shaft 122, to couple the eccentric shaft 122 to the piston 130.

FIG. 2 is an enlarged view showing a region A of FIG. 1. As shown in FIG. 2, the main bearing 126 of the cylinder block 124 has the annular thrust surface 160 on the upper surface thereof. The thrust surface 160 extends in a direction perpendicular to the center axis of the main bearing 126. The center of the thrust surface 160 conforms to the center axis of the main bearing 126. The inner diameter of the thrust surface 160 is greater than the inner diameter of the main bearing 126. An annular extending section 162 is provided between the inner circle of the thrust surface 160 and the inner surface of the main bearing 126. The annular extending section 162 has a cylindrical shape extending in the longitudinal direction. The axis of the annular extending section 162 conforms to the axis of the main bearing 126. The inner surface of the annular extending section 162 is continuous with the inner surface of the body of the main bearing 126 and faces the outer peripheral surface of the main shaft 120.

The thrust ball bearing 176 is placed on the outer side of the annular extending section 162 of the main bearing 126, between the flange 174 of the shaft 118 and the thrust surface 160 of the main bearing 126. The thrust ball bearing 176 has a plurality of balls 166. The balls 166 are rolling elements. The plurality of balls 166 are equal in size to each other. The balls 166 are held in a cage 168. Instead of the thrust ball bearing 176, other ball bearings such as a roller bearing may be used.

The cage 168 is an annular flat plate member and is made of a resin material such as polyamide. The cage 168 has an inner surface which is in contact with the outer surface of the annular extending section 162 and includes a plurality holes inside thereof. The plurality of holes are arraigned in a circumferential direction thereof. The balls 166 are rollably stored in the holes, respectively. The height of the cage 168 is smaller than the diameter of the balls 166. The balls 166 protrude upward and downward from the cage 168. The balls 166 are sandwiched between an upper race 164 and a lower race 170 from above and from below, and held therein.

The upper race 164 and the lower surface 170 are annular flat plate members, and are made of a metal, preferably, a spring steel or the like which has been subjected to a thermal treatment. The upper and lower surfaces of each of the races 164, 170 are parallel to each other and are formed to be flat. The upper race 164 is placed above the balls 166 and the cage 168. The upper surface of the upper race 164 is in contact with the lower surface of the flange 174, while the lower surface of the upper race 164 is in contact with the balls 166. The lower race 170 is placed below the balls 166 and the cage 168. The upper surface of the lower race 170 is in contact with the balls 166, while the lower surface of the lower race 170 is in contact with the upper surface of a support member 172. The support member 172 is positioned below the lower race 170.

The support member 172 is an annular member having an elasticity. The upper surface of the support member 172 is in contact with the lower surface of the lower race 170, while the lower surface of the support member 172 is in contact with the thrust surface 160 of the main bearing 126. The inner diameter and the outer dimension D of the support member 172 are set so that the support member 172 is located below the balls 166. The thickness (longitudinal dimension in cross-section) t of the support member 172 satisfies a relationship of 0.1 d<t<0.3 d with respect to the diameter d of the main shaft 120 of the shaft 118.

FIG. 3 is a perspective view showing a wave washer 172 used in the thrust ball bearing 176. As the support member 172, for example, an annular wave washer of FIG. 3 is used. The wave washer 172 is formed of a spring steel, and is curved alternately upward and downward in a thickness direction thereof. The wave washer 172 includes a plurality of (two in the present embodiment) upper convex portions 172 c, 172 d protruding toward the lower race 170 (FIG. 2) and a plurality of (two in the present embodiment) lower convex portions 172 a, 172 b protruding toward the thrust surface 160 (FIG. 2) of the main bearings 126 such that they are arranged alternately in the circumferential direction. The upper convex portions 172 c, 172 d are connected to the lower convex portions 172 a, 172 b by smooth curves. The number of the upper convex portions and the number of the lower convex portions in the wave washer 172 are not limited to two so long as the upper convex portion and the lower convex portion are arranged alternately in the circumferential direction.

Next, the operation of the sealed compressor 100 as described above will be described. As shown in FIG. 1, a power supply (not shown) such as the power supply utility provided outside the sealed container 102 is connected to the power supply terminal 113 of the sealed container 102. Thus, AC power is supplied from the outside power supply to the electric component 110. In the electric component 110, the rotor 116 rotates by a magnetic field generated in the stator 114. Concurrently, the main shaft 120 of the shaft 118 fastened to the rotor 116 rotates and the eccentric shaft 122 coupled to the main shaft 120 via the flange 174 rotates eccentrically.

The coupling section 136 converts the eccentric rotation motion of the eccentric shaft 122 into a linear reciprocation motion. The piston 130 reciprocates inside the compression chamber 148 of the cylinder 134. According to the motion of the piston 130, the volume of the compression chamber 148 closed by the piston 130 changes. When the piston 130 moves in the direction for increasing the volume of the compression chamber 148, the working fluid flows from the suction pipe 103 into the sealed container 102 and is suctioned into the compression chamber 148 via the suction muffler 152. On the other hand, when the piston 130 moves in the direction for reducing the volume of the compression chamber 148, the working fluid is compressed in the compression chamber 148 and then the working fluid in high-temperature and high-pressure states is sent from the sealed container 102 to a refrigeration cycle (not shown) via the discharge pipe 105 or the like.

When the main shaft 120 rotates, the lubricating oil 104 is suctioned up by a centrifugal force by the lower portion of the main shaft 120 and the pump section. By the centrifugal force and a viscosity, the lubricating oil 104 is fed to sliding sections of the compression component 112 through the oil feeding mechanism 128. This makes it possible to reduce a friction and an abrasion of the sliding sections.

When the flange section 174 rotates, the balls 166 of the thrust ball bearing 176 roll while point-contacting the upper race 164 and the lower race 170. This makes it possible to reduce a friction between the thrust surface 160 of the main bearing 126 and the lower surface of the flange 174 of the shaft 118. Because of this, a driving power loss due to the friction can be reduced, and the mechanical efficiency of the sealed compressor 100 can be improved.

In the thrust ball bearing 176, the support member 172 receives a load applied in the longitudinal direction to the flange 174 by the shaft assembly 118 a. Furthermore, in a state in which the shaft 118 and the rotor 116 are rotating, the support member 172 receives a longitudinal thrust of the electric component 110. For example, when the shaft 118 is inclined, a biased load is applied to the support member 172. At this time, the support member 172 is displaced to a great degree at a region where the load is great, and is displaced to a small degree at the other region, thereby absorbing the biased load. When the sealed container 102 receives an impact, an instantaneous great force as well as the load of the shaft assembly 118 a is applied to the support member 172. In this case, the entire or a part of the support member 172 is deformed in the thickness direction, to absorb an instantaneous great force. As should be understood, the support member 172 perform an aligning function and an impact absorbing function by its elasticity, so that the contact load between the balls 166 and the races 164, 170 can be maintained in a proper range. Thus, the friction and plastic deformation of the balls 166 are reduced, and the thrust ball bearing 176 stably maintains the rotation of the shaft 118. Thus, the mechanical efficiency of the sealed compressor 100 can be improved. Moreover, the friction between the balls 166 and the races 164, 170 can be reduced, and generation of a noise and a vibration can be prevented.

Note that the shaft assembly 118 a is likely to resonate due to the support member 172 having a longitudinal elasticity. In general, a one-dimensional resonance frequency f of an elastic material with a spring constant k and a mas m is expressed as f=(1/2π)*(k/m)⁻0.5. In the present embodiment, the support member 172 with the spring constant K bears the load of the shaft assembly 118 a. Therefore, the shaft assembly 118 a resonates if it rotates with a frequency of (1/2π)*(K/M)⁻0.5.

In contrast, the sealed compressor 100 operates such that the maximum rotational frequency F of the compression component 112 including the shaft 118 satisfies a relationship of F<(1/4π)*(K/M)⁻0.5. This makes it possible to prevent the resonance of the shaft assembly 118 a. Specifically, FIG. 4 is a graph showing a frequency response function of the shaft assembly 118 a. A horizontal axis indicates the rotational speed (rotational frequency) [Hz] of the shaft assembly 118 a per unit time, while a vertical axis indicates a magnitude [dB] of a power spectrum. The magnitude [dB] of the power spectrum indicates the magnitude of a vibration.

As indicated by a peak A in the frequency response function of FIG. 4, the resonance frequency f of the shaft assembly 118 a is 140 Hz, and is expressed as (1/2π)* K/M)⁻0.5 as described above. On the other hand, the sealed compressor 100 operates such that the maximum rotational frequency F of the shaft assembly 118 a is smaller than resonance frequency f and the maximum rotational frequency F satisfies the relationship of F<(1/4π)*(K/M)⁻0.5. For example, in the sealed compressor 100 of the present embodiment, as indicated by “operation range” of FIG. 4, the rotational frequency of the shaft 118 is 27 Hz to 70 Hz, and its maximum rotational frequency F is 70 Hz. Thus, the sealed compressor 100 operates in a range in which 70 Hz as the maximum rotational frequency F of the shaft 118 is smaller than ½ of 140 Hz as the resonance frequency f of the shaft assembly 118 a. Because of this, the shaft 118 does not vibrate significantly by the resonance due to the support member 172. Therefore, it becomes possible to prevent an increase in the vibration and a noise caused by this increase in the vibration, in the sealed compressor 100.

In the frequency response function of FIG. 4, a peak B which is the frequency 10 Hz is the resonance frequency of the compressor body 106 suspended by the suspension spring 108 inside the sealed container 102, and is not the resonance frequency f of the shaft assembly 118 a. The frequency 10 Hz of the peak B is much lower than 27 Hz which is the minimum rotational frequency of Embodiment 1. Therefore, the compressor body 106 does not resonate, and as a result, a noise and a vibration do not increase in the sealed compressor 100.

According to the relationship between the resonance frequency f and the maximum rotational frequency F of the shaft assembly 118 a, i.e., F<(1/4π)*(K/M)⁻0.5, as the spring constant K of the support member 172 increases, the maximum rotational frequency F of the shaft 118 increases. However, the longitudinal spring constant K of the support member 172 with the outer diameter D, the thickness t, and a Young's modulus E of the spring steel, is expressed as K∝Et⁻3/D⁻2. According to this formula, the spring constant k of the support member 172 is proportional to a cube of the thickness t and is inversely proportional to a square of the outer diameter D. The outer diameter D of the support member 172 is defined by the diameter d of the main shaft 120 of the shaft 118. The Young's modulus E of the support member 172 is Young's modulus E of the spring steel. It is difficult to change this Young's modulus E. Because of this, the outer diameter D and Young's modulus E of the support member 172 are substantially constant, and therefore, the thickness t of the support member 172 is inevitably increased to increase the spring constant K of the support member 172. This is undesirable because the height of the sealed compressor 100 increases. Therefore, to make the sealed compressor 100 thinner, the thickness t of the support member 172 is set so that t<0.3 d is satisfied with respect to the diameter d of the main shaft 120 of the shaft 118. This makes it possible to increase the maximum rotational frequency F of the shaft 118 while avoiding the resonance of the shaft assembly 118 a, and suppressing the height of the sealed compressor 100.

By comparison, if the thickness t of the support member 172 is set too small, then the longitudinal spring constant of the support member 172 becomes too small. In light of this, the thickness t of the support member 172 is set to satisfy 0.1 d<t with respect to the diameter d of the main shaft 120 of the shaft 118. In this setting, even when a transient vibration load is applied in the longitudinal direction to the balls 166 of the thrust ball bearing 176, the support member 172 is elastically deformed, and is able to absorb the transient vibration load well. Therefore, it becomes possible to prevent a situation in which the balls 166, and the upper race 164 and the lower race 170 which are in contact with the balls 166 collide against each other and a dent is formed there. Hence, it becomes possible to prevent a reduction of reliability of the sealed compressor 100, and an increase in the vibration and the noise in the sealed compressor 100, which would otherwise be caused by the dent.

In a case where the operation of the sealed compressor 100 is controlled by an inverter power supply, the maximum rotational frequency F of the shaft assembly 118 a may be set to a frequency which is higher than a power supply frequency. Specifically, when the electric power is supplied from the inverter power supply to the electric component 110, the inverter power supply adjusts the frequency of the supplied electric power. In response to the frequency of the AC power which is adjusted by the inverter power supply, the rotational frequency of the rotor 116 of the electric component 110, and the rotational frequency of the shaft 118 fastened to the rotor 116 change. The rotational frequency is a value preset continuously or plural values preset in a stepwise manner, and may be set to a frequency which is equal to or higher than the frequency of the electric power supplied from the power supply. Thus, if the maximum rotational frequency F of the shaft assembly 118 a is higher than the power supply frequency, a vibration force due to the rotation increases in proportion to a square of the rotational speed, and a vibration acceleration in the case of the resonance is very great. However, since the resonance of the shaft assembly 118 a is avoided, it becomes possible to prevent an increase in the vibration and the noise, in the sealed compressor 100.

Embodiment 2

FIG. 5 is a cross-sectional view schematically showing a refrigerator 178 according to Embodiment 2. As shown in FIG. 5, the refrigerator 178 includes a heat-insulating casing 180 having a heat-insulating space inside thereof and doors attached to the heat-insulating casing 180 to open and close the heat-insulating space. The surface of heat-insulating casing 180 attached with the doors is a front surface and the opposite surface is a back surface.

The heat-insulating casing 180 has a substantially rectangular parallelepiped shape which is elongated in the longitudinal direction. The heat-insulating casing 180 includes a heating insulating wall defining the heat-insulating space inside thereof, and partition plates for partitioning the heat-insulating space into a plurality of (five in the present embodiment) heat-insulating space sections 188, 190, 192, 194, 196. The five heat-insulating space sections 188, 190, 192, 194, 196 are vertically separated as four stages. The heat-insulating space section in the second stage from the upper is separated into two parts in a rightward or leftward direction. For example, the heat-insulating space section in the first stage from the upper is used as a chill room 188, the two heat-insulating space sections in the second stage from the upper are used as a switch room 190 and an ice making room 192, the heat-insulating space section in the third stage from the upper is used as a vegetable room 194, and the heat-insulating space section in the fourth stage from the upper is used as a freezing room (compartment) 196. The heat-insulating space sections 188, 190, 192, 194, 196 are connected to each other via ducts (not shown), and dampers are provided inside the ducts. The ducts allow air communication among the respective heat-insulating space sections. The flow rate of the air is adjusted by the dampers. The heat-insulating space sections 188, 190, 192, 194, 196 are partially or entirely provided with temperature sensors (not shown).

The heat-insulating casing 180 includes an inner casing 182 and an outer casing 184 provided outside the inner casing 182. The inner casing 182 is manufactured by vacuum-molding using a resin such as ABS. The inner casing 182 constitutes the inner surface of the heat-insulating wall defining the heat-insulating space and the partition plates for partitioning the heat-insulating space. The outer casing 184 is made of metal such as a pre-coat steel plate, and constitutes the outer surface of the heat-insulating wall. A heat-insulating material 186 is unitarily foamed and filled in a space formed between the inner casing 182 and the outer casing 184, thus constructing the heat-insulating casing 180. In this way, the heat-insulating wall and the partition plates are formed together and unitarily. As the heat-insulating material 186, for example, foamed plastic such as a hard urethane foam, a phenol foam, or a styrene foam is used. As this foamed material, for example, a hydrocarbon-based cyclopentane is used to prevent global warning.

The heat-insulating casing 180 is provided with a recess 208 formed by denting a part of its back surface and its upper surface. The sealed compressor 100 is elastically supported in the recess 208. A condenser (not shown) and a drier (not shown) for removing a moisture are placed on the side surface or the like of the heat-insulating casing 180. In addition, a capillary 212 which is a pressure-reducing unit and an evaporator 216 are placed on the back surface of the heat-insulating casing 180. A cooling fan 214 and the evaporator 216 are placed on the back surface of the vegetable room 194 and the back surface of the freezing room 196 in the interior of the heat-insulating casing 180. The sealed compressor 100, the condenser, the capillary 212 and the evaporator 216 are connected together in an annular shape by a pipe 218, thus constituting a refrigeration cycle. Furthermore, the heat-insulating casing 180 is provided with a controller (not shown). The temperature sensors placed in the heat-insulating space sections are connected to the controller. In addition, the sealed compressor 100, the condenser, the drier, the capillary 212, the evaporator 216, the cooling fan 214 and the evaporator 216 are connected to the controller. The controller controls these components based on the detection values of the temperature sensors.

In the present embodiment, five doors 198, 200, 202, 204, 206 are attached to the heat-insulating casing 180 such that the doors 198, 200, 202, 204, 206 can open and close the front surfaces of the heat-insulating space sections 188, 190, 192, 194, 196 in the interior of the heat-insulating casing 180. The chill room 188 is provided with a rotatable door 198, while the switch room 190, the ice making room 192, the vegetable room 194, and the freezing room 196 are provided with drawing doors 200, 202, 204, 206, respectively. The rotatable door 198 and the drawing doors 200, 202, 204, 206 are each constructed by bonding a decorative sheet to the heat-insulating material such as foamed polystyrene. Between the doors 198, 200, 202, 204, 206 and the heat-insulating casing 180, gaskets are placed, which can keep the heat-insulating space sections 188, 190, 192, 194, 196 in a sealed state.

Next, the operation of the refrigeration cycle of the above described refrigerator 178 will be described. The controller starts and stops the cooling operation based on the detection signals from the temperature sensors. Upon the start of the cooling operation, the working fluid is compressed by the reciprocation motion of the piston 130 (FIG. 1) in the sealed compressor 100, and the working fluid in the high-temperature and high-pressure states is sent from the discharge pipe 105 (FIG. 1) to the refrigeration cycle through the pipe 218. The gaseous working fluid in the high-temperature and high-pressure states radiates heat in the condenser, and is condensed into a liquid. The liquid working fluid is pressure-reduced in the capillary 212 to be turned into low-temperature and low-pressure states, and reach the evaporator 216. The cooling fan 214 operates to cause the air in the vegetable room 194 and the freezing room 196 to migrate, and this air exchanges heat with the working fluid in the low-temperature state in the evaporator 216. The working fluid raises its temperature and is evaporated. The evaporated working fluid is returned to the sealed compressor 100 through the pipe 218. In contrast, the cooled air is delivered to the heat-insulating space sections 188, 190, 192 via the ducts. At this time, the flow rates of the cooled air delivered to the heat-insulating space sections 188, 190, 192 are adjusted via the dampers, so that the heat-insulating space sections 188, 190, 192, 194, 196 are adjusted at proper temperatures, respectively.

For example, the temperature of the chill room 188 is a temperature at which stuff are not frozen and preserved in a chilled state, for example, 1 to 5 degrees C. The switch room 190 is set to a temperature which can be changed by the user, and is placed at the set temperature. This set temperature may be set to, for example, a specified temperature in a range from a temperature zone of the freezing room 196 to a temperature zone of the vegetable room 194. The ice making room 192 includes an automatic ice making device (not shown), and is configured to automatically make ice and reserve the ice. To preserve the ice, the ice making room 192 is adjusted at a temperature which is relatively higher than the freezing temperature zone, for example, minus 18 to minus 10 degrees C. The vegetable room 194 is adjusted at a temperature which is equal to or slightly higher than that of the chill room 188, for example, 2 to 7 degrees C. As this temperature is lower and is not a freezing temperature, the freshness of the vegetables can be kept for a long time. The freezing room 196 is normally adjusted at minus 22 to minus 18 degree C. to preserve stuff in a frozen state. However, to preserve the stuff in a more frozen state, for example, the freezing room 196 may be adjusted at minus 30 to minus 25 degree C.

In the operation of the refrigeration cycle, the sealed compressor 100 is operated so that the maximum rotational frequency F satisfies a relationship of F<(1/4π)*(K/M)⁻0.5. Since the rotational frequency of the shaft assembly 118 a is lower than the resonance frequency f of the shaft assembly 118 a due to the wave washer 172, the resonance of the shaft assembly 118 a can be prevented. As a result, an increase in a noise and a vibration in the sealed compressor 100 can be prevented, and a noise in the refrigerator 178 can be reduced.

In the sealed compressor 100, a driving power loss caused by the friction of the thrust ball bearing 176 can be suppressed. This can reduce an energy loss in the refrigerator including the sealed compressor 100.

In the sealed compressor 100, the thickness t of the wave washer 172 satisfies a relationship of 0.1 d<t<0.3 d. This can lessen the height of the sealed compressor 100, and reduce a size of the heat-insulating space in the interior of the refrigerator 178. In addition, denting of the balls 166 in the thrust ball bearing 176 can be prevented, a reduction of the reliability of the refrigerator 178 can be prevented, and a vibration and a noise in the refrigerator 178 can be reduced.

Since the partition plates and the heat insulating wall in the heat-insulating casing 180 are constructed by unitarily filling the foamed material, a cost reduction and improvement of a heat insulating capability can be achieved. Since the partition plates manufactured in this way have a heat-insulating capability which is about twice as high as that of the heat-insulating member of the foamed polystyrene, the partition plates can be thinned, and correspondingly the heat-insulating space can be expanded.

Other Embodiments

Although in Embodiment 1, the compression component 112 is placed above the electric component 110, it may be placed below the electric component 110. In this case, the thrust ball bearing 176 is placed between the rotor 116 and the thrust surface 160 of the upper end of the main bearing 126, while the support member 172 is placed between the lower race 170 and the thrust surface 160.

Although in Embodiment 2, the sealed compressor 100 is incorporated into the refrigerator 178, it may be used in a device using a refrigeration cycle (heat pump cycle) such as an air conditioner and an automatic dispenser.

Although in Embodiment 2, the partition plates and the heat-insulating wall are formed unitarily in the heat-insulating casing 180, they may be formed separately.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a sealed compressor which can reduce an energy loss and a noise, a refrigerator including the sealed compressor, etc.

REFERENCE SIGNS LIST

100 sealed compressor

102 sealed container

110 electric component

112 compression component

114 stator

116 rotor

118 shaft

120 main shaft

122 eccentric shaft

124 cylinder block

126 main bearing

130 piston

134 cylinder

148 compression chamber

160 thrust surface

166 ball (rolling element)

168 cage

164 upper race (first race)

170 lower race (second race)

172 support member

172 wave washer

172 a, 172 b lower convex portion (convex portion)

172 c, 172 d upper convex portion (convex portion)

174 flange

176 thrust ball bearing (ball bearing)

178 refrigerator 

1. A sealed compressor comprising: an electric component including a stator and a rotor which is rotatable with respect to the stator; a compression component activated by the electric component; and a sealed container accommodating the electric component and the compression component; wherein the compression component includes: a shaft including a main shaft fastened to the rotor, an eccentric shaft which is eccentric with respect to the main shaft, and a flange connecting the main shaft and the eccentric shaft to each other; a cylinder block including a main bearing supporting the main shaft such that the main shaft is rotatable, and a cylinder having a compression chamber inside thereof; a piston which is coupled to the eccentric shaft and is reciprocatable within the compression chamber; and a ball bearing placed between the flange and a thrust surface of the main bearing; wherein the ball bearing includes: a cage; a plurality of rolling elements held in the cage; a first race and a second race which sandwich the rolling elements therebetween; and an elastic support member placed between the second race and the thrust surface of the main bearing; and wherein when a mass of a shaft assembly including the rotor and the shaft is M, a spring constant of the support member is K, and a maximum rotational frequency of the shaft assembly is F, a relationship of F<(1/4π)*(K/M)⁻0.5 is satisfied.
 2. The sealed compressor according to claim 1, wherein the support member is an annular wave washer; and Pe wherein the wave washer is configured to include a plurality of convex portions protruding in a thickness direction toward the second race and a plurality of convex portions protruding in the thickness direction toward the thrust surface of the main bearing such that the convex portion protruding toward the second race and the convex portion protruding toward the thrust surface are arranged alternately.
 3. The sealed compressor according to claim 2, wherein the wave washer is formed of a spring steel; and wherein when a diameter of the main shaft is d and a thickness of the wave washer is t, 0.1 d<t<0.3 d is satisfied.
 4. The sealed compressor according to claim 1, wherein the electric component is activated by one of a plurality of operation frequencies using an inverter power supply which adjusts a frequency of electric power supplied to the electric component.
 5. A refrigerator comprising the sealed compressor as recited in claim
 1. 